Composite anode for x-ray tubes



May 28, V1929. Q T ULREY ET AL 1,715,151

COMPOSITE ANODE FOR X-RAY TUBES Filed Sept. 19, 1.925

lupon the X-ray tube Patented May 28, 1929.

UNITED :STATES PATENT oFFic-E.

CLAYTON VlItIIlrLE ULREY, F EAST ORANGE, AND vLQUIS E. EHR-KE, "0FNEWARK, NEW JERSEY, ASSIGNORS T0 WESTINGHOUSE LAMP COMPANY, A.CORPORATION I 0F PENNSYLVANIA.

COMPOSIAlTE ANODE FOR X-RAY TUBES.

Application led September 19, 1925. Serial No. 57,271.

rllhis invention relates to X-ray tubes and lmore particularly to suolitubes adapted for diagnostic purposes.

The present invention is an improvement shown in co-pending application,Serial No. 38,395, iiled Junel 20, 1925, assigned to the presentassignee and to the X-.ray tubes disclosed by the other applicationsreferred to in said co-pending application.

Our invention and improvement relates 'to the provision in an X-ray tubeof the type disclosed in said co-pending applications of means forexternal coolingand 'more specili- Ically to the construction oftheanode .unit for securing good heat conduction whereby a greater energyinput may be utilized with advantageous results.

In view of the foregoing it is an object of the present invention toprovide an X-ray tube of the type disclosed in said co-pendingapplication Tvith external cooling means.

Another object of the invention 1s to provvide 'an anode constructionenabling the expeditious assembly and sealing thereof in the envelope-orcontainer of an X-ray tube.

A further .and more specific object of our invention is to provide ananode consisting of a plurality of parts certain of which are ofldifferent metals and Which are so united and assembled that good headconduction is obtained from the target end of the anodefto the other orradiator end.

@ther vobjec-tsof the invention will be apparent as the followingdescription of the in- ,vention is read.

A better understandingvof the invention may be obtained by lreferring tothe accompanying draiving in which:

Fig. 1 is a cross-sectional view of an -ray vtube embodying theinvention and Fig. 2 is a detailed vieu1 of the anode assembly.

Referring to Fig. 1 of thevdraiving an X- ray tube embodying ourinvention may comprise a glass envelope 3 of cylindrical'shape to whichis sealed at 4 avreentrant tube Which has its end 6 extending in closeproximity to tlieend of the container or envelope 3. Enclosing the end 6of the reentrant tube 5 and supported vthereby is an'inverted cup-shapedmetallic screen member 8, said member having a relativelysmall opening 9in the-end IThe body l12 has Wall Wall 11 thereof. The end G of thereentrant ltube supports a cup-shaped body 12 of insulating material bymeans of an outwardly projecting fiange 13 integral with said body.

le having small circular opening 15 therein, said opening being in linewith the longitudinal anis of the X-ray tube` Disposed Within theinsulating body 12 is a filament or electron-emitting cathode 16 b entin the form of a spiral having a centrally disposed opening 17 whichopening is also in axial alignment with the longitudinal axis of theX-ray tube. The ends 18 and 19 of the iilamentary cathode pass throrghapertures 21 and 22, respectively, in a mica disk 23 and through opening241 and 25, respectively, in the Wall 11 of the metallic member orscreen 18. The mica disl 23 has a central opening 26 therethrouglralsoin axial alignment With the longitudinal axis ofthe tube.

The ends 18 and 19 of the lilamentary cathode are Welded or otherwisesecured to leading-in Wires 27 and 28, respectively, said Wires beingvhermetically sealed in the glass Walls of the envelope 3 or else inpresses' 29 and 31 of stems 32 and 33 fused 'to the Walls of theenvelope 3. The leading-in Wires 27 and 28 maybe secured to contact caps2T and 28 respectively.

The above described structure is fully disclosed and claimed in theco-pending applications referred to heretofore and forms no Vpart of thepresent invention except where claimed in combination with featuressubsequently to 'be'disclosed rlhe present invention, as statedheretofore, relates more particularly to constructing the anode in suchmanner as to provide for external cooling and also to simplify as Wellas to reduce the cost of assembly of the component parts of the tube.

The anode as aWhole is designated by the numeral 34 and comprisesessentially three parts, namely,-the target portion 35, the seal portion36 and the radiator portion 37.

The tarlret portion consists of a solid rod or copper or other goodheating-conducting moterial which 'has a head portion 38 having arounded end 39 in which is secured by threading or otherwise a target l1of good ray-radiating material, such thorium and the like.v A reducedshank 12 extends from the head portion, said shank having a.

Y the target portion to the seal portion 36.

' a pressure the saine,

CII

v tion 47 The seal portion 36 may consistof a rod 'ofcopperlhaving avthreaded aperture or recess 46 in one end for receivingthe threaded end44 of the target portion and an enlarged portion at the opposite endwhich also has a threaded recess for securing the seal portion to theradiator portion 37. The enlargedpor has an annular iange '49 extendingtherefrom, said flange being sufficiently thin so that it will stretchand will not exert such upon the glass as tosliear. or break inches hasproven satisfactory. It is well known that copper or its'oside will wetglass as to form an hermetic seal therewith.

rIhe radiator portion 37 comprises a` shank 510il aluminum having` athreaded end.A 52 for engaging the threaded recess 48 and having theother end 53reduced in 4cross-section. A brass sleeve 54 is forcedoverthe reduced end 53 ofthe shank and supports a plurality of radiatingvanos or fins 55 of disk-shape spaced apart by washers 56 which latterare clamped to brass sleeve 54 between flanges 5T integral with thelatter. The end 58 of the brass sleeve 54 engages ashoulder 59 on theshank 5l. ployed to more firmly securev the radiator on .the shank. Theradiator portion 37 may, if

desired, be cast in one piece and be made of aluminum. K Y Y Y Theadvantages secured by constructing the anode in three parts areasfollows:

It is desirable to make the seal portion 36 as a separate unit as itprevents injury Y through oxidation of the target since in seal- Vingthe seal portion 36 to glass it is necessary to" heat the copper toaliigh temperature. lllhere the target portion is separate at the timesuch operation is performed, the heat thus necessary to affect thesealing can not reach the target inasmuch as such operation Vcan be madewhile the two parts are separated. It is also advantageous to make theseal portion separate from the'standpoint of economy, since in the eventof afaulty or damaged seal the main part of the target is Y not lost. lnaddition the seals may be made separately and tested before assemblingthe parts of the anode.

It is of advantage to make the radiator porl tion separate from the sealportion in order to facilitate the construction and to save material andlabor in case of a faulty oi damaged seal. l

rlhe heat conduction from the target to the radiator during operation ofan X-ray tube embodying the present anode construction is not materiallyimpaired by such construction as the threaded unions between the partsare VVso constructed that the thermal contact iin- Y proves with rise 1ntemperature. As will VA thickness of from .008 to .O12V

A washer 61 and screw 62 may be embecomes heated through electronicimpact upon the target 41, the copper rod 42 expands and since the heat`is flowing from this portion toward theradiator it is obvious; that saidportion will be at a more elevated temperature than the seal portion 36,owing to this difference intemperature and the disposition of the end of44 of the target portion'in the recess 46 of the seal portion it isobvious that the threaded end of the rod will expand into firm contactwith the threads of the recess 46, thus providing forgood heatconduction through this connection.

Conduction of the heat between the 'seal portion 36 and the radiatorportion 37 is facilitated by making the portion 5l of the latter o-faluminum. Owing tov aluminumV having a greater coefficient of expansionthan that of copper of which the seal portion is made, it is obviousthat contact between the threaded end 52 and threaded recess 43iinproves as the temperature rises, VA .further advantage in the use ofaluminum is that on account of its low density thestress on the seals,due Ato the weight of the radiator, is consideably less than if copperor a heavier metal were used. Y

The anode 34 may be supported within the envelope by means of af sleeve63 of metal which may have an interiorly threaded collar 64 integraltherewith for connection to the threaded portion 43 on the targetportion V35. The sleeve 63 is of such size as to frictionally lengagethe inner surface of the reentrant tubeV Theseal portion 36 through thethin annul lar flange 49 may be hermetically sealed-at 6T to a flare 68which in turn may be fused tof the envelope 3 at 69. i Y

As set forth more fully in the co-pending application above identified,the tube may be evacuated in any suitable manner and thereafter mercuryvapor orl an inert gas admitted thereto at about one micron pressure. Inaddition the spacing of the electrodes with respect to each other andthe distance between the anode and inner `wall of the reentrant tube .5should be such thatno appreciable gaseous ionization occurs. Thefunctions of the variousparts of the' device except the anodestructureand the manner in which'the same operates -isl more fully set forthinthe co-pendingV applications heretofore referred to and inasmuch asthese form no part of the present invention no detailed explanation isessential 'to a full understanding thereof. It will also be noted thatby reason ofthe construction described X-rays generated are taken outvofthe tube along its longitudinal axis.

Modicationsof the invention Willroccur to those skilled in the art,however' such modiiications are contemplated as come Within the spiritand scope of the invention as defined by the appended claims.

7hat is claimed is:

l. An anode for an X-ray tube of the character described comprising a`target portion, a seal portion removably secured to said target portion,and a radiator portion, said seal and target portion being composed ofthe same material and the former having an opening in which said targetportion is itted.

2. An anode for an X-ray tube of the character described comprising atarget portion of copper, a seal portion of copper and a radiatorportion of aluminum, said target and radiator portions being secured insaid seal portion, and said seal portion having an opening in which saidtarget portion is fitted.

3. An anode for X-ray tubes and the -like comprising a rod of copper, aseal portion of copper having a recess for receiving the end of saidrod, and a radiator portion of aluminum secured to said seal portion.

4:. An anode for an X-ray tube comprising a rod of copper having atarget in one end thereof and being threaded at the other end, a sealportion consisting of a threaded recess at one end for receiving thethreaded end of said rod, a sea-ling iiange` extending from the otherend of said seal portion, and an aluminum rod secured in thelast-mentioned end of said seal portion, said aluminum rod having aradiator secured thereto;

5. An anode for an X-ray tube comprising three parts, one partconsisting of a rod of copper having a rounded end with a targetinserted therein and the other end being threaded, and a threadedportion intermediate the ends of said rod, another part of said anodeconsisting of a rod of copper having a recess in each end thereof and anannular flange extending from one end, said iange being relatively thinand serving to forni a seal with glass, and the third part of said anodeconsisting of a rod having one end threaded and having a radiatorsecured to the other end.

6. An X-ray tube comprising an envelope, a reentrant tube therein andfused at one end thereto, an anode housed Within said tube, Said anodecomprising an anode-portion having a target in one end thereof and meansfor supporting said anode upon the inner side of said tube, and a sealportion secured to said anode portion, said seal portion having a flangefor hermetically sealing said envelope to said seal portion.

7. An X-ray tube comprising an envelope, a cathode and an anode therein,focusing means adjacent said anode and cathode, said anode comprising arod of good heat conducting material, a sealing portion threadedlyengaging the end of said rod, and a radiator portion threadedly engagingsaid sealing portion and means on said rod for supporting the sameWithin said envelope.

In testimony whereof, We have hereunto subscribed our names thiseighteenth day of September, 1925.

CLAYTON TRIDLE ULREY. LOUIS F. EHRKE.

